Convection schemes

The additional source terms which bring about the different convection schemes are
activated by means of PATCH and COVAL commands in which

The VALUE argument in COVAL command specifies which scheme is to be used.

The patch NAME is used to select the coordinate direction in which the scheme is
introduced and the nature of damping algorithm, i.e. the composite- blending or composite
bounded.

PATCH commands contain the special names, types and can cover the computational domain
in user prescribed order.

(i) Patch name

To activate any of the schemes available, the patch name must start with four
characters CONM. A fifth character controls the coordinate direction in which the scheme
is to be applied, as follows:-

PATCH name

Scheme in the direction

CONM2

All

CONM3

X

CONM5

Y

CONM7

Z

However, if the sixth character of the patch name is the letter D, then it signifies
the choise of the one of the local oscillation- damping algorithms, i.e SOLD or CDLD,
depending on the GRNDn number in the value argument of the COVAL command, as will be
explained in the next section. The letter C in the sixth character of the patch name
determines the CSOB scheme to be used. In the latter case two different PATCH'es with the
names ending with C0 and C4 followed by corresponding COVAL commands must be specified for
each variable.

(ii) Patch type

The patch type must be CELL.

(iii) Extent

The extent of the patch does not need to be the whole computational domain, but will
determine the region over which the scheme is applied.

Note that convection terms are modified only over the cell surfaces internal to the
patch.

The COVAL command has the general format

COVAL ( CONM***, phi, FIXFLU, GRNDn )

where

(i) phi is a scalar variable;

(ii) The GRNDn number in the value argument determines the scheme to be used, according
to the following table:

Value

PATCH name

Scheme

GRND

CONM*

Implicit SOUD

GRND4

CONM*

Implicit CDS

GRND4

CONM*D

Implicit CDLD

GRND

CONM*D

Implicit SOLD

GRND

CONM*C0

Implicit CSOB

GRND4

CONM*C4

Users may choose to employ different schemes for different variables; they may do so
simply by setting different GRND numbers in their corresponding COVAL statements. The
coefficient argument of the COVAL is always FIXFLU.

For example, a Q1 file which invokes the fully implicit SOLD algorithm over the whole
integration domain for a variable UC1 would include the statements:

PATCH ( CONM2D, CELL, 1,NX,1,NY,1,NZ,1,LSTEP)

COVAL ( CONM2D, UC1, FIXFLU, GRND )

But, the PATCH and COVAL commands to activate the CSOB in X- direction would be , as
follows :